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Hit'n'Mix Infinity

Unmixing & Spectral Resynthesis Software
By Robin Vincent

The chorus from Radiohead's 'Sulk' as viewed in Infinity.The chorus from Radiohead's 'Sulk' as viewed in Infinity.

Infinity is no ordinary audio editor, but one that allows you to manipulate the individual instruments within a mixed audio file in endless ways.

It's a remarkable thing to see a mixed piece of music pulled apart and displayed as individually editable instruments. Through the use of its TrueSource source-separation technology, Infinity from Hit'n'Mix can identify the tonal qualities of instruments and split music into fully adjustable notes and percussion. It has the look and feel of Melodyne in some respects, but presents multiple instruments in a single view and allows their individual identities to be blurred, cloned, blended and transplanted. It's not an easy program to explain and it feels like it's yet to fully nail down its own identity, but there's some very clever stuff going on in here.

Hit'n'Mix Infinity does its magic through sinusoidal spectral analysis and resynthesis. What you see on screen are not audio tracks: they are resynthesized representations of musical data created with component sine waves, referred to by Hit'n'Mix as Rips. The process of ripping is not, as I had initially assumed, one of generating multiple individual audio tracks from mixed audio; rather, it is one of gathering and analysing audio data and identifying musical notes, timbres and tonal qualities. So, the first thing you need to understand is that you are not dealing with audio files but their component ingredients; and until you change something, these recombine perfectly to make an exact copy of the original audio file.

To Rip a file or files, you simply drag and drop them into the Infinity window. Unless you have a fast computer, the process can take a long time, but fortunately the ripper can do its work in the background.

Building Blocks

Developer Martin Dawe declines to explain what's going on behind the scenes; my closest point of reference is the recent electric piano releases from virtual instrument developers Sampleson. Instead of modelling circuitry or sampling the sound of, say, a Fender Rhodes, they have done deep-level spectral analysis, down to the frequency and amplitude of individual sine waves. The full range of sounds can be recreated by combining the right sine waves in the right way, resulting in a very authentic-sounding Rhodes from only a few megabytes of sine waves.

Martin says that his inspiration came from a David Attenborough piece about the Australian lyrebird, which mimics the sounds of other birds as part of its mating call. The remarkable thing is that the lyrebird will mimic anything it hears — not just birdsong, but all sorts of environmental sounds. The documentary shows it doing strangely convincing imitations of camera shutters, car alarms and chainsaws cutting down trees. Martin was inspired to figure out how to break down any sound to something simple and manipulable like sine waves, creating an algorithmic model based upon the way people perceive notes. He's been rolling this around for about 17 years and Infinity sees these ideas made concrete in a piece of software that's incredibly detailed, versatile and unlike anything else out there.

Infinity's ability to pull out individual instruments within mixed music is extraordinary.

So, what can you do with it? That is the question. In essence, Infinity unlocks the DNA of audio and gives you the flexibility to manipulate it at a molecular level. Sound is not being emulated and audio is not being streamed or processed: you are applying algorithms to the component elements of sound. These algorithms, or RipScripts as they are called, are written in the Python programming language, and you can get down and dirty with the code directly within Infinity. The RipScripts define the notes and describe the musical elements, dictating how the elements are put back together and what happens when you process them. This could be as simple as adding a vibrato effect to a vocal or as mind-bending as applying the tonal qualities and harmonic content of a clarinet to the sound of a guitar.

Multitrack Remixing

Infinity's ability to pull out individual instruments within mixed music is extraordinary. There's a lot of fun to be had with it, and there's much potential for fixing and tweaking things. It could be useful with live recordings where you want to fix a bum note or maybe remove noise and other artifacts. You can do interesting things like isolating and copying a vocal line from one song and placing it...

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Published January 2020